Grinding Machine Contact Detection via Motor Control Axis Signals
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Solution Overview
Problem
Existing machine tools face challenges in accurately detecting contact between a grindstone and a workpiece, particularly in fine contact states, due to difficulties in distinguishing changes in current command values and feedback values during grinding operations.
Innovation Solution
A machine tool configuration that includes a tool holder, workpiece holder, actuator control circuitry, motor control circuitry, and contact detection circuitry, where the contact between the grindstone and workpiece is detected based on changes in motor control values, specifically using a motor with a control axis that crosses the tool rotation axis and movement direction, allowing for accurate detection of contact even in fine contact states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact detection is performed using current command value changes, then contact between grindstone and workpiece can be detected, but detection accuracy is insufficient in fine contact states
Solution Approach 1:
The patent introduces a motor with a control axis that serves as an intermediary measurement system. Instead of directly measuring contact force or current changes, the system uses the motor's control value changes along a specific axis (crossing both the tool rotation axis and movement direction) as an indirect but more sensitive indicator of contact. This intermediary measurement approach enables detection of fine contact states that were previously undetectable using direct current monitoring.
Solution Approach 2:
The patent changes the measurement parameter from general current command value changes to specific motor control value changes along a defined control axis. By selecting a motor whose control axis crosses both the tool rotation axis and the movement direction, the system captures more sensitive parameter variations that occur during fine contact, thereby improving detection accuracy and reliability.
2Measurement precision
If a motor with control axis crossing tool rotation axis and movement direction is used, then contact detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent employs a motor that serves multiple functions: it controls holder movement along the control axis, enables contact detection through control value monitoring, and provides positioning capability. By selecting a motor whose control axis naturally crosses both the tool rotation axis and movement direction, the system achieves contact detection functionality without requiring additional specialized sensors or measurement devices, thus limiting the increase in device complexity.
3Measurement precision
If contact detection sensitivity is increased to detect fine contact states, then detection capability improves, but signal stability at non-contact times deteriorates
Solution Approach 1:
The patent applies local quality by selectively monitoring control values along a specific control axis rather than analyzing all motor parameters globally. The control axis is specifically oriented to cross both the tool rotation axis and the movement direction, creating a localized measurement zone where contact-induced variations are most pronounced. This focused monitoring approach enhances detection sensitivity for fine contact while filtering out unrelated signal variations that would otherwise degrade stability during non-contact periods.
Data Source
AI summary
A machine tool includes a tool holder configured to hold a grindstone. A workpiece holder is configured to hold a workpiece. At least one actuator is configured to move the tool holder in a movement direction relative to the workpiece holder. A motor is different from the at least one actuator and is configured to move one holder out of the tool holder and the workpiece holder along a control axis. Actuator control circuitry is configured to control the at least one actuator to move the tool holder in the movement direction. Motor control circuitry is configured to control the motor to control the one holder to be stationary in a direction along the control axis. Contact detection circuitry is configured to detect a contact between the grindstone and the workpiece based on a change in a control value of the motor.